rexford

German face-hardened armor had very variable resistance in some firing tests conducted by Americans against 30mm German FHA plates. But I think I know why the penetration and resistance models don't seem to jive, cause the 80mm armor was bolted on and wasn't face hardened everywhere. Thomas Jentz' latest book on Panthers has detailed drawings that show where plates were face-hardened, and the face-hardening was not applied to the edges where the armor would be welded (Panther rear hull plate was face-hardened, which we didn't know). Holes in a plate lower the resistance, and who knows what happens when face-hardening is not applied around the edges. Some of what Jason C says does suggest that 30mm over 50mm on Pzkpfw IV and StuG III might resist like less than 80mm of FHA plate, although the examples he presented in the past for 30mm/30mm on PzKpfw IIIH front seemed to support more than 60mm equivalent resistance. There is info that suggests one thing and other factoids that support the other side. I do find it odd that 500m is the magic range for 76.2mm against 80mm FHA, and not 400m or 600m.

Jason C posted some good data bites: "pp 74-76 says with the long 75, fire at enemy AFVs at ranges beyond 1500m was discouraged as ineffective and a waste of ammo, because AP would fail to penetrate even with a hit." 75L48 APCBC would penetrate T34 glacis at 1700m with high hardness armor factor (-24%) and no side angle, based on our calculations. Jentz' Panzertruppen Volume 1 has a similar figure for 75L43. Some reports in Jentz limit 75L43 range against T34 glacis to 1000m, while Valera Potapov read a Russian firing test report where 75L43 penetrated T34 glacis at 1000m with a 30 degree side angle. I doubt we'll ever get one final answer for 75L48 penetration range against T34 glacis. At 1500m, 75L48 APCBC hits on T34 turret front and mantlet would probably succeed. "p. 84 says the 80mm front models "could withstand the fire of the 76.2mm tank gun of the Russian T-34 if it did not come within 500m." Says the same was true for the ZIS-3. It also mentions a weakness in the gun cradle armor, only 45-50mm (much like the turret of a Pz IV incidentally)." Based on our calculations, 76.2mm BR-350B APBC penetrates 75mm of face-hardened armor at 500m. At 500m, the ratio of penetration divided by armor resistance would allow some successes. 76.2mm APCR could easily defeat 80mm face-hardened at 500m. What date does the above quotation refer to: would 76.2mm APCR be available at the time? The flat plate assembly which protected the gun innards was 50mm thick, and very vulnerable. "p. 87 discussing the StuH talks about its weakness vs. enemy armor, because the low muzzle velocity of its HEAT ammo made it effective only at 500m. "At distances under 500m, as was already noted elsewhere, the front armor of the assault gun offered no protection from the fire of tank guns." No protection, or an ability to defeat many of the hits? "No protection" implies all hits succeeded. Maybe they were referring to 76.2mm APCR. "p. 117 says flatly that the 75L48 with Pz Gr 39 could not penetrate the IS-2 from the front, even at a range of 100m. Nearby, an AAR mentions a StuG killing an IS-2 with its 5th hit after the first 4 bounced, without specifying which plate was struck." The author of that statement could be referring to the front hull of IS-2 Model 1944. The 110mm mantlet and 100mm turret front would seem vulnerable if one hit where the curvature was low and the range was 500m or so. "p. 127 shows an 80mm front StuG-IV model with track sections on its bow and concrete reinforcements." Hits on face-hardened armor tend to severely damage the plates if the penetration is close to the resistance, so anything that slows the round helps insure good armor condition. By the time StuG IV arrived the number of 85mm guns on the Ostfront was probably considerable, and APCR would be more common.

With a one man turret crew, the rate of fire probably would be much lower than what would be attained with a field gun. If the tank were trying to hit a moving across the line of fire target then the rate of fire goes down even more since the turret guy has to estimate target lead, rotate the turret with the moving tank and then jump ahead to the necessary lead, pull the trigger, watch the fall of shot and hit result, go back for more ammo on misses or bouncers and start the lead thing again, etc. And if the first target is knocked out, how long to pick up on another target and start the firing procedure. One man turrets would probably have many drawbacks including rate of fire. [ August 03, 2003, 06:42 PM: Message edited by: rexford ]

Following site has breakdown of hits on damaged Panthers by gun size, most hits and penetrations of Panther flank armor at Kursk seem 76.2mm field guns (or tanks?): http://www.battlefield.ru/library/bookshelf/losses/losses6.html 45mm hits and penetrations occurred.

When actual firing tests are conducted, the effect of slope is found to be much larger than the "thickness/cosine(slope angle)" equation predicts. The above formula gives the straight line horizontal distance through a sloped plate. Projectiles penetrate by first being slid so the nose points upwards, then they penetrate going downward. The energy they lose going through all of that results in an increase in effective thickness. We did a mathematical study of how slope effect differs with plate thickness and projecile diameter. When 2 pdr AP hits 40mm at 40 degrees the effective vertical thickness is about 64mm, a 1.6 slope multiplier. When 17 pdr AP hits 40mm at 40 degrees the effective vertical thickness is about 56mm, a 1.4 slope multiplier. 2 pdr AP is a smaller round and 40mm/40 degree plate is better able to change the rounds' flight path than the heavier 17 pdr (2.38 pounds vs 17 pounds projectile weight), so 2 pdr AP has larger slope multipliers. When 17 pdr AP hits 80mm at 40 degrees the vertical resistance is about 64mm, a 1.6 slope multiplier. The U.S. and British curves are rough estimates while we found the true relationship, which is a function of angle and the "plate thickness/projectile diameter" ratio. [ July 24, 2003, 06:13 PM: Message edited by: rexford ]

Slope Effect Curves Basic Stuff Russian Flat Nose APBC 10 degrees, 1.02 multiplier 15 degrees, 1.03 20 degrees, 1.06 25 degrees, 1.11 30 degrees, 1.17 35 degrees, 1.25 40 degrees, 1.42 45 degrees, 1,60 50 degrees, 1.75 55 degrees, 2.00 60 degrees, 2.20 Pointed Nose AP and U.S. APBC 10 degrees, 1.02 15 degrees, 1.06 20 degrees, 1.13 25 degrees, 1.20 30 degrees, 1.25 35 degrees, 1.40 40 degrees, 1.60 45 degrees, 1.82 50 degrees, 2.00 55 degrees, 2.20 60 degrees, 2.75 The above slope effects are estimates since they are heavily dependent upon the plate "thickness/projectile diameter" ratio. A rough estimate can also be obained by assuming that the penetration equations are straight lines between the points given in the game. If a round penetrates 100mm at 0 degrees, 80mm at 30 degrees and 42mm at 60 degrees the 20, 45 and 55 degree penetration estimates would be: 20 degrees 100 -(100-80) x (20/30) = 87mm 45 degrees 80 - (80-42) x (15/30) = 61mm 55 degrees 80 - (80-42) x (25/30) = 48mm The exact solutions would be: 20 degrees, 89mm 45 degrees, 63mm 55 degrees, 50mm

Thank you for going beyond my mere speculation and adding some factual stuff. So, does brittle armor resist 95mm HEAT like good quality plate?

Sexy Rexy was my father's nickname among the women in the neighborhood. The slope effects for AP and flat nose APBC will be posted tomorrow evening, after my Viagara treatment. [ July 16, 2003, 05:51 PM: Message edited by: rexford ]

Yes but Andy, this is just another point in the M4s favour in a comparison with the T-34, which is the point of this thread. With this line of thinking the T-34 can't actually be compared with the PIII and PIV chassis since they were much earlier designs. But that being said one could make an indirect comparison of the T-34 and M4 by comparing them to their WWII opponents. For example did the initial design objective of creating a Medium tank impervious to the PaK37 met in Spain find completion in the T-34? </font>

Sherman 75mm gun is much better than T34 76.2mm in terms of face-hardened and homogeneous armor penetration (if T34 does not have alot of APCR at the time), and the U.S. HE is really good. T34 76.2mm might have a slightly better accuracy edge on paper given the higher muzzle velocity, but Sherman APCBC is heavier and carries better with range, and that three man Sherman turret crew results in a more efficient and effective command capability. And Sherman turret rotation is really fast, while T34 turret motor is not the most dependable thing around.

What if the plates in contact are in perfect contact at all points? Brinell Hardness is measured by pushing a ball into the plate surface and measuring the dimensions of the indentation. The harder the plate the less of a dent, and the higher the attraction between molecules. I guess hardness indicates molecular bond strength in some way, and the greater the bond strength the more heat is needed to break the bonds and melt the metal. So for a given temperature harder metals are more difficult targets (the pressure at the tip of the HEAT jet is due to high temperature?). Hardness doesn't relate to more resistance against APCBC because brittleness enters the picture along with stress waves.

Made the mistake of playing Panthers and Churchill VIII's in the same scenario, where 95mm HEAT wiped the Panthers off the board. The 95mm HEAT penetration of 125mm vertical is enough to penetrate 80mm/55 degrees with 85% quality (which equals 119mm vertical). Brittle armor does not always correlate with reduced HEAT resistance. T34 high hardness 45mm plates lose 24% of resistance against 75mm APCBC compared to medium hardness armor, but gain about 10% more resistance than medium hardness armor against HEAT due to the greater difficulty in burning through harder plate. Panther glacis is medium hardness armor and brittle behavior would come from inclusions, laminations and bad byproducts from the hardening process. So the question is whether the bad things in some Panther glacis armor that reduce resistance to AP, APCBC and APBC would also hurt when HEAT hits the plate. I recently came across a British tanker discussion where one fellow said 95mm HEAT was not very good against tanks. With a 1650 fps muzzle velocity 95mm HEAT hits might be hard to obtain on the first or second shots, which might account for the low effectiveness against armor. Since the brittle areas within the Panther glacis seem to have had about the same hardness as the good areas, it is possible that HEAT resistance may not be compromised by brittle medium hardness armor unless there are laminations (internal areas that are like several plates in contact instead of a single plate). Do several plates in contact resist HEAT with the same effectiveness as a single plate with similar thickness? [ July 14, 2003, 05:00 PM: Message edited by: rexford ]

I've read where armor piercing caps are supposed to reduce ricochet chances. Analysis of slope effects shows that pointy nose AP has lower slope effects than APCBC, which suggests that the APCaps aren't doing much biting into the armor. The armor piercing cap against sloped armor may fall into the same caregory as the curved cast hull front on M4A1 that is supposed to present superior armor resistance, two theories that may not hold water. [ July 14, 2003, 04:38 PM: Message edited by: rexford ]

Yup, you beat me to it. German 50mm ammo consisted of AP and APC. AP was a pointed nose projectile without any caps, the German 50mm AP had an explosive filler. APC for 50mm gun had an armor piercing cap that also served as a ballistic windscreen, since it improved the air resistance of uncapped AP. But the APC air resistance was not as low as APCBC, so 50mm APC loses velocity at a good clip. APCBC is an armor piercing round with an armor piercing cap, and both are under a ballistic cap windscreen that improves the aerodynamics. German 75mm L24 round had one cap that functioned as both an armor piercing cap and a ballistic cap. Normally armor piercing caps have a square looking nose, but on the 75mm L24 round the armor piercing cap was sleek and aerodynamically well shaped. Armor piercing caps are designed to decrease the probability of nose shatter against hard armor and face-hardened plates, and to reduce shatter possibilities. There is a good chance that early German ammo, such as 37mm and 50mm AP, was softer and uncapped and may have shattered on Russian and British thick armor. The armor piercing cap fits over the nose and shoulder of the projectile, often with an air space between the cap and the projectile nose. When the round hits armor the initial impact is spread over the projectile shoulder and very little makes it to the nose, so shatter and nose damage chances are minimized. British 2 pdr AP shattered alot against German face-hardened armor in Africa. Armor piercing caps improve penetration against face-hardened armor, since that type of armor defeats hits by damaging the nose and body of the round. If the nose and body of the ammo is slightly damaged or untouched, the face-hardened armor is in trouble. U.S. 75mm APCBC penetrates about 105mm of face-hardened armor at 0m and vertical, Sherman 75mm AP penetrates about 95mm. But armor piercing caps absorb energy against homogeneous armor and decrease the penetration: 75mm APCBC from Sherman penetrates 91mm homogeneous armor at vertical and 0m, 75mm AP penetrates 114mm. Homogeneous armor is the same hardness all the way through (more or less), face-hardened has a thin layer that is very hard.

Just remember that the slope effects I posted are for German capped ammunition (47mm and 50mm APC, 75mm, 88mm and upwards APCBC). If you want I'll post some slope effects for uncapped AP and APBC, which is what the Russians used.

The Americans used standard slope effects for all rounds as a function of angle, which went something like this: 10 degrees from vertical, 1.01 multiplier 15 degrees, 1.03 20 degrees, 1.07 25 degrees, 1.15 30 degrees, 1.25 35 degrees, 1.37 40 degrees, 1.52 45 degrees, 1.69 50 degrees, 1.89 55 degrees, 2.13 60 degrees, 2.50 For source, go to http://salts.britwar.co.uk/mod.php?mod=fileman&menu=8&PHPSESSID=467d5558481062a2dd0a4e84f50196d8 WW II weapon penetration tables. then go down page to WO 185/118. Suggest you use the above figures for a quick conversion of 0 degree penetration to angled performance, but only for APC and APCBC ammo. [ July 13, 2003, 06:53 PM: Message edited by: rexford ]

Why estimate penetration at angles using straight line horizontal distance when some better figures are available? Slope effect for APCBC ammo, such as most German rounds of 47mm and greater diameter, varies with the thickness of the plate divided by the projectile diameter. Here are some sample figures to go by, which are based on analysis of firing test results: 75mm plate at 30 degrees ======================== 95mm vertical vs 50mm APC (1.27 slope effect) 92mm vertical vs 75mm APCBC (1.23 slope effect) 91mm vertical vs 88mm APCBC (1.21 slope effect) 75mm plate at 45 degrees ======================== 139mm vertical vs 50mm APC (1.85 slope effect) 131mm vertical vs 75mm APCBC (1.75 slope effect) 127mm vertical vs 88mm APCBC (1.69 slope effect) 60mm plate at 50 degrees ======================== 128mm vertical vs 50mm APC (2.13 slope effect) 118mm vertical vs 75mm APCBC (1.97 slope effect) 114mm vertical vs 88mm APCBC (1.90 slope effect) 60mm plate at 55 degrees (Panther nose) ======================================= 157mm vertical vs 50mm APC (2.62 slope effect) 141mm vertical vs 75mm APCBC (2.35 slope effect) 136mm vertical vs 88mm APCBC (2.27 slope effect) 80mm plate at 55 degrees (Panther glacis) ========================================= 226mm vertical vs 50mm APC (2.83 slope effect) 203mm vertical vs 75mm APCBC (2.54 slope effect) 195mm vertical vs 88mm APCBC (2.44 slope effect) 60mm plate at 60 degrees (Hetzer glacis) ======================================== 193mm vs 50mm APC (3.22 slope effect) 175mm vs 75mm APCBC (2.92 slope effect) 168mm vs 88mm APCBC (2.80 slope effect) The above slope effects do not apply to uncapped pointed nose AP or Russian flat nose APBC which has a windscreen to reduce air resistance. Slope effects used in above example do not apply to tungsten core ammo. Note that when 17 pdr APCBC hits Panther glacis (76.2mm round), penetration is not going to occur unless the round hits a weld line or gets a lucky break (in the brittle armor that some Panthers carried).

The effective resistance of angled armor is not a function of the horizontal thickness that is presented. Using geometry and trig, a 60mm plate at 60 degrees from vertical presents a horizontal distance of 120mm to incoming rounds. However, projectiles don't penetrate sloped armor on a straight line, they do all sorts of odd things. If U.S. 76mm APCBC hits armor at 60 degrees from vertical, the round first starts to ricochet so the nose points upward, and then it tries to drive down a plug so the ammo would actually defeat the plate going downward if it was successful. No straight line here. 60mm at 60 degrees slope resists U.S. 76mm APCBC like 173mm of vertical plate, so Hetzers are safe from M10's on glacis hits. 76mm APCBC hits would ricochet off harmlessly, even against poor quality plate. When flat nosed Russian APBC hits 60 degree armor, the flat nose digs in and resists the ricochet effect, and twists the round so it lines up closer to the armor perpendicular. When Russian 76.2mm hits 60mm at 60 degrees the armor resists like 163mm vertical, when 122mm APBC hits 60mm/60 degrees the vertical resistance is 98mm, so projectile diameter and weight play a part. If 122mm APCBC (post WW II) and 122mm APBC hit 60mm at 60 degrees, the vertical resistances are 155mm (vs 122mm APCBC) and 98mm (vs flat nose APBC). Tungsten core ammo is very hard and brittle, so angled armor is a real problem since it snaps the round and causes fracture. U.S. 76mm HVAP against 60mm at 60 degrees is resisted by a vertical plate equivalency of 267mm. U.S. 76mm HVAP bounces off the Hetzer glacis plate at point blank unless the armor is deficient. [ July 13, 2003, 08:22 AM: Message edited by: rexford ]

500 yard penetration of U.S. machine gun bullets: cal. .30 AP M2 ============== 166 grains 24" barrel 2775 feet per second muzzle velocity 0.302" homogeneous (7.7mm) 0.190" face-hardened (4.8mm) cal. .50 AP M2 ============== 708 grains 36" and 45" barrel 2835 and 2935 feet per second muzzle velocity shorter barrel 0.742" homogeneous (18.8mm) 0.530" face-hardened (13.5mm) longer barrel 0.790" homogeneous (20.1mm) 0.595" face-hardened (15.1mm) If the outer plate on the 50mm Pak gunshield succeeded in shattering the bullets or blunted their tips, it might result in a boost of the armor resistance over the sum of the two shield thicknesses. When two plates are spaced, homogeneous armor resistance will be less than the sum of the plates unless the outer plate shatters or blunts the projectile before it hits the inner armor. Source for above data is TM9-1907, Ballistics Data: Performance of Ammunition (1948)

True, but T34 track is also wider than Sherman. Ground pressures follow: T34 Model 1943, 10.7 psi T34/85 Model 1944, 11.1 psi M4A2 Sherman, 14.4 psi M4A2(76) Sherman, 15.1 psi Sherman track is kind of narrow for the weight. PzKpfw IVG and IVH have ground pressures of 11.9 and 12.6 psi, considerably less than M4A2's. If the Russians needed to get somewhere fast in snow, mud or other soft ground conditions, Shermans might not be the tank of choice. I also believe that Shermans were more prone to tipping over on side slopes, something the Russians may have commented on and which occurred quite a bit in practice. Some time ago it seemed to me that the Tiger and Panther had less longitudinal track length between wheels, which might provide better flotation. With more wheels, the pressure points directly under the tracks would not be as peaked and might be reduced. That was one of my misconceptions that was never pursued very far. While the height of the Sherman is usually treated as a drawback, makes it a better target, in high wheat fields the Americans found that the greater turret height made it easier to see over the fields (while making the tank easier to see in return). Didn't the Shermans have an advantage over T34 in terms of better ventilation or heating for the crew? And finally, German tankers noted that T34/76 (models 41, 42 and 43) was virtually blind to the sides and rear due to: 1. two man turret where commander is very busy 2. large main turret hatches on Models 41 and 42 which discouraged unbuttoned observation on the move 3. bubbly vision glass on sides of turret without magnification Eventually a German POW explained the problem to the Russians and they put cupola's on T34 Model 43. [ July 12, 2003, 08:42 AM: Message edited by: rexford ]

Russian anti-tank rifles could penetrate about 30mm at close ranges.

Prior to having duckbills installed on the Sherman tracks, that tank was not very good on soft ground. Report to Eisenhower notes that Tiger, Tiger II and Panther drove easily over soft ground that caused Shermans all sorts of problems. Russian cross country driving test showed that PzKpfw IIIG was much faster than the T34 with a four speed transmission, and slightly faster than the five speed tranny T34.

The difference between German and British gun shields is the type of armor. Germans used face-hardened armor on the shields, British didn't. Face-hardened armor becomes more and more effective against hits, compared to homogeneous armor, as the projectile diameter decreases. Spaced plates on the shield might also defeat rifle bullets by having the first plate blunt the nose of the round, which decreases the performance against the second plate. Firing tests with 57mm through 90mm ammo also show that a thin spaced plate in front of the main armor can shatter the round and reduce ability against main armor. [ July 11, 2003, 09:08 PM: Message edited by: rexford ]

Now that's a super response, Bastables. Great work in summarizing just about everything. Thanks for working so hard. "I'd like to point out that when T-34 85 met M4A3E8 in Korea the M4 came out on top. "T-34 July Nov 1950 Dealing with 223 T-34 Hulks Armour=89 Destroyed 8 damaged (the M4 destroyed 41) Air=27 Destroyed 2 damaged Arty/Mortar=20 Destroyed 8 damaged Infantry Weapons=24 Destroyed 15 Damaged Captured/unknown=63."" Does the report have any details as to penetration ranges against T34 armor by particular rounds?

Sherman gun wasn't better than T34 gun, in fact 75mm on M4 fired AP and APCBC at 619 m/s versus 655 and 662 m/s for T34. Difference was projectile hardness and the armor piercing caps on APCBC. It was better Sherman ammo. Sherman fired uncapped solid shot AP at 619 m/s with 55 Rockwell C nose hardness, and it penetrated 115mm vertical homogeneous armor at 0m. With armor piercing cap on APCBC, Sherman round penetrated 105mm face-hardened and 91mm homogeneous at 0m and vertical. T34 76.2mm APBC penetrated 84mm face-hardened at 0m with typical round and 81mm homogeneous due to softer nose than Sherman even though muzzle velocity was 655 m/s. T34 solid shot uncapped AP round, which was very rare, defeated 106mm homogeneous and 92mm face-hardened at 0m and vertical, which makes it better than Sherman 75mm APCBC and close to 75mm AP M72. Russians loved Shermans cause they could penetrate Tiger side armor, 76.2mm APBC could not do it on a consistent basis. With APCR a T34 gains a little, but round is not the most accurate and not plentiful. U.S. armor plate very poor till late 1943, T34 uses brittle high hardness armor throughout war.